%I A001687 M0147 N0059
%S A001687 0,1,0,1,0,1,1,1,2,1,3,2,4,4,5,7,7,11,11,16,18,23,29,34,45,52,68,81,102,
%T A001687 126,154,194,235,296,361,450,555,685,851,1046,1301,1601,1986,2452,3032,
%U A001687 3753,4633,5739,7085,8771,10838,13404,16577,20489,25348,31327
%N A001687 a(n) = a(n-2) + a(n-5).
%D A001687 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001687 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001687 T. M. Green, Recurrent sequences and Pascal's triangle, Math. Mag., 41 
               (1968), 13-21.
%H A001687 <a href="Sindx_Tu.html#2wis">Index entries for two-way infinite sequences</
               a>
%H A001687 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=405">
               Encyclopedia of Combinatorial Structures 405</a>
%H A001687 S. Plouffe, <a href="http://www.lacim.uqam.ca/%7Eplouffe/articles/MasterThesis.pdf">
               Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures</
               a>, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 
               1992.
%H A001687 S. Plouffe, <a href="http://www.lacim.uqam.ca/%7Eplouffe/articles/FonctionsGeneratrices.pdf">
               1031 Generating Functions and Conjectures</a>, Universit\'{e} du 
               Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
%H A001687 E. Wilson, <a href="http://www.anaphoria.com/meruone.PDF">The Scales 
               of Mt. Meru</a>
%F A001687 G.f.: x/(1-x^2-x^5).
%F A001687 G.f. A(x) satisfies 1+x^4A(x) = 1/(1-x^5-x^7-x^9-....) - Jon Perry (perry(AT)globalnet.co.uk), 
               Jul 04 2004
%p A001687 A001687:=-z/(-1+z**2+z**5); [S. Plouffe in his 1992 dissertation.]
%o A001687 (PARI) a(n)=if(n<0,polcoeff(x^4/(1+x^3-x^5)+x^-n*O(x),-n),polcoeff(x/
               (1-x^2-x^5)+x^n*O(x),n)) /* Michael Somos, Jul 15 2004 */
%Y A001687 Cf. A005686.
%Y A001687 Sequence in context: A144693 A029139 A100927 this_sequence A159072 A116928 
               A034391
%Y A001687 Adjacent sequences: A001684 A001685 A001686 this_sequence A001688 A001689 
               A001690
%K A001687 nonn
%O A001687 0,9
%A A001687 N. J. A. Sloane (njas(AT)research.att.com).